Method of making propeller tips



March 29, 1949 w. c. HEATH 2,465,872

METHOD OF MAKING PROPELLER TIPS Filed July 17, 1943 William C.Heath INVENTOR.

ATTORNLYI Patented Mar. 29, 1949 METHOD OF MAKING PROPELLEB TIPS William 0. Heath, Shorewood, Wis assignor to A. O. Smith Corporation, Milwaukee, Wis., a corporation of New York Application July 17, 1943, Serial No. $95,155

4 Claims.

' 1 This invention relates to a method of making propeller tips.

The principal object of the invention is to provide a method of forming a tip section by flattening of a tubular blank of substantially circular section.

Another object of the invention is to provide a method of more accurately forming a tip sect on.

Another object is to provide a method of forming a tip section adaptable to the forming of high strength alloy steel blades.

Other objects and advantages-of the inventio appear hereinafter in connection with the description of an embodiment of the invention illustrated in the accompanying drawing.

In the drawing:

Figure l is a perspective view of a cylindrical blank from which the tip section is made;

Fig. 2 is a similar view of the blank after forming the same to a conical shape and providing the edge ridges thereon;

Fig. 3 is a similar view after hot coining of the blank;

Fig. 4 is a view showing the hot forging of the edges wherein they are given the twist required;

Fig. 5 is a longitudinal section through the wall of the blank after machining;

Fig. 6 is a schematic end view of the pressing operation for drawing the edge ridges;

Fig. 7 is a similar view of the pre-spreading operation;

Fig. 8 is a similar vew of the first flattening operation;

Fig. 9 is a similar view of the final flattening operation;

Fig. 1c. is an end elevation of the formed tip section; and

Fig. ii is a side elevation of the formed tip section showing the remaining parts of the propeller blade assembled and welded thereto.

In the manufacture of hollow steel propeller blades of high strength low alloy steel, as set forth in applicants copending application, Serial No. 480,682, filed March 26, 1943, for Electrically welded hollow steel propeller blade and method of making the same, the accurate forming. of the tubular tip section has been difficult. The thinness of the section in many cases, particularly at its outer end, has discouraged attempts to make the same of longitudinally welded parts similar to the body section of the propeller.

The forming of a tip section from a cylindrical blank by flattening also presents difliculties, particularly with high strength alloys of the type now sought to be employed in propellers. Attempts ,to collapse a cylindrical tube of the dimensions required without injury to the surface have generally resulted in failure heretofore.

In carrying out the present invention a cylindrical blank v l is first machined to a proper tapered thickness and then formed as by spinning or rolling to a conical shape to provide the conical blank -2 of Fig. 2. A pair of side ridges 3 are provided diametrically opposite each other and extending for the full length of the blank.

The ridges 3 may be formed by machining if a blank of sufficient thickness is employed or may be extruded as by upsetting the side wall between dies. The specific manner of obtaining them is relatively unimportant.

The blank 2 is then hot coined to bilge it as shown in Fig. 3 and provide a shape more nearly. corresponding to that of the final blade section, except that the body of the blank is still circular in crosssection. After bilging of the blame, the ridges are hot forged between dies that provide the required twist in the blank, as illustrated in Fig. 4', to provide a blank in which the ridges will correspond in location with the final twisted leading and trailing edges of the blade section. The inside of the blank is then cam bored to provide a wall thickness of the order of that illustrated in I Fig. 5.

Figs. 6 to 9 illustrate the flattening of the blank Fig. 6, consists of the hot drawing of the ridges? or edges, as they are sometimes referred to; For this purpose the blank is heated to between 2000?" F. and 2200"v F and placed in a vertical'press with a thin plate mandrel 4 extending between the ridges 3 and having a rib 5 on each of its upper and lower edges twisted to correspond with the position of the ridges. Dies 6 are brought to bear vertically upon the blank and have channels in their respective die faces for receiving the corresponding ridges 3. In this operation the ribs 5 form a channel in the inside surface of the blank beneath each ridge 3 and effect a coining of the ridges. The channel thus formed serves to provide a predetermined inside curvature for the edges of the finished blade section and prevents tearing of the metal in subsequent forming operations.

Fig. 7 illustrates the pre-spreading operation in which the blank is expanded edgewise by a two-part inside mandrel l in line with the edges 3 of the blank. In this operation the metal is tensioned, chiefly adjacent the ridges 3 so as to 3 overcome any tendency of it to kink at this point in later forming operations.

blank are pressed inwardly by dies 9. The opera-'- tions are simultaneous so that there is .a progressive stretching and forming of the metal of the walls of the blank between the two ridges 8.

The second and final flattening step is illustrated in Fig. 9 and is substantially the same as that shown in Fig. 8 except for the shape of the die parts and blank. After flattening the blank is hot contour formed as in suitable coining dies embodying substantially the shape of the final blade section. It is trimmed at the ends and is then ready for assembly and welding to other sections it of the blade as indicated in Fig. 11.

The weight distribution and shape of the tip section is more accurately controlled by the mechanical spreading of the blank accompanied by the lateral forming of its side walls than is possibleunder other types of forming. The method of the present invention is not dependent upon sealing the ends of the blank, as when internal flu d pressure is employed to support the blank against collapse. The heat of the blank is retained without difficulty for forming although with the alloy employed the blank should be heated to a temperature of from 2000 F. to 2200 F. for each of the flattening operations.

The process is particularly adaptable to the forming of blanks of low alloy high strength steel which is ordinarily more difficult to form than plain carbon steel.

The invention may have various embodiments within the scope of the accompanying claims.

I claim:

1. In the manufacture of a longitudinal sec-9 tion of a propeller blade, the steps of forming a tubular blank with one end smaller than the other and with a pair of lateral ridges thereon disposed with the pitch twist of the final blade to correspond to the leading and trailing edges.

thereof, die forming a channel on the internal surface of the blank to correspond with each ridge, collapsing the blank between successive pairs of dies to an air foil shape having the pitch twistof the blade, and internally supporting said blank during collapse solely in a direction at right angles to'the movement of the dies by mechanical means engaging the blank in said channels and positively radially stretching and forming said blank in the direction of said ridges.

2. In the manufacture of a longitudinal section of a propeller blade, the steps of forming a tubular blank with one end smaller than the other and with a pair of lateral ridges thereon disposed 4 with the pitch twist of the final blade to correspond to the leading and trailing edges thereof, die forming a channel on the internal surface of the blank to correspond with each ridge, positively radially stretching and forming the blank in the direction of said ridges by mechanical means engaging in saidchannels, and thereafter simultaneously continuing said expanding and collapsing of the side walls of the blank to air foil shape.

3. In the manufacture of longitudinal sections of propeller blades, the steps of forming a tubular blank with one end smaller than the other and with a pair of lateral ridges thereon disposed to correspond to the leading and trailing edges thereof, forming a channel on the internal surface of the blank to correspond with each ridge by pressing the ridges of the blank in a generally radial direction onto a fixed die mandrel, collapsing the blank between succesive pairs of dies to an air foil shape having the pitch twist of the blade, and internally supporting said blank during collapse solely in a direction at right angles to the movement of the dies by mechanical means engaging the blank in said channels and positively radially stretching and spreading said blank in the direction of said ridges.

4. In the manufacture of a longitudinal section of a propeller blade. the steps of forming a hollow blank wth a pair of external ridges disposed thereon with the pitch twist of the final blade to correspond to the leading and trailing edges thereof, forming a channel on the internal surface of the blank to correspond with each ridge, and thereafter distending the areas of said blank between said ridges in the directions thereof by mechanical means engaging said channels and simultaneously therewith collapsing the blank by external means to the desired foil section and pitch twist of the blade.

WILLIAM C. HEATH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 756,832 Cleveland Apr. 12, 1904 1,478,480 Iowe Dec. 25, 1923 1,892,712 Taylor Jan. 2, 1933 2,138,127, Squires Nov. 29, 1938 2,308,344 I Andrake Jan. 12, 1943 FOREIGN PATENTS Number Country I Date 346,455 Germany Jan.,2, 1922 

